1. Field of the Invention
The present invention relates to an analyzer which can easily determine the presence or absence of a target analyte in a sample through immunoassay or the like.
2. Background Art
The presence or absence of a target analyte in a sample has hitherto been determined by bringing the sample into contact with a substance capable of specifically binding to the target analyte and detecting a binding reaction between the target analyte and the substance . Examples of such a technique include in immunological technique by virtue of an antigen-antibody reaction and a hybridization technique for determining the presence or absence of a target sequence through a hybridization with a specific oligonucleotide.
With respect to the immunological technique, various methods are known wherein a liquid sample is brought into contact with a carrier having a surface on which an antibody capable of specifically binding to an antigen has been immobilized and a labelled antibody is allowed to treat the carrier, thereby determining the presence of an antigen in the liquid sample.
For example, Japanese Patent Laid-Open No. 127160/1988 discloses an apparatus wherein a membrane having an antibody bound thereto in a spot form is put on the top surface of a cylindrical container and the lower portion is filled with a highly hygroscopic substance. In this apparatus, at the outset, a liquid sample is added, and an antibody labelled with a gold colloid particle is dropwise added thereto. If the liquid sample contains an antigen in a detectable concentration or more, a reddish purple spot is observed.
Similar apparatuses are disclosed in Japanese Patent Publication Nos. 502214/1986 and 25551/1988. In these apparatuses, it is necessary to conduct two steps, i.e., the step of adding a liquid sample to the membrane portion for allowing the liquid sample to be absorbed into the membrane and the step of dropwise adding a labelled antibody solution. Thus, the procedure may become complicate. Further, in these apparatuses, the membrane easily dries. It is unfavorable for the membrane to easily dry, because this gives rise to a difference in the results between immediately after the reaction and after drying. Further, when the liquid sample is a urine or feces suspension or the like, an apparatus having the surface of the membrane which is exposed to air even after the reaction is unsanitary. Moreover, the apparatus having the surface of the membrane which is exposed to air is unsuitable for transportation.